Alfred Russel Wallace (1823–1913) was a British naturalist, explorer, geographer, anthropologist, and biologist. He is best known for independently proposing a theory of natural selection which prompted Charles Darwin to publish on his own theory. Wallace did extensive fieldwork, first in the Amazon River basin and then in the Malay Archipelago, where he identified the Wallace Line that divides Indonesia into two distinct parts, one with animals more closely related to those of Australia and the other with animals more closely related to those found in Asia. He was considered the 19th century's leading expert on the geographical distribution of animal species and is sometimes called the "father of biogeography". Wallace was one of the leading evolutionary thinkers of the 19th century who made a number of other contributions to the development of evolutionary theory besides being co-discoverer of natural selection. These included the concept of warning colouration in animals, and the Wallace effect, a hypothesis on how natural selection could contribute to speciation by encouraging the development of barriers against hybridization. (Full article...)